In mammals, olfactory sensory perception is mediated by two anatomically and functionally distinct sensory organs: the main olfactory epithelium (MOE), and the vomeronasal organ (VNO). Pheromones activate sensory neurons within the VNO to elicit a characteristic array of innate reproductive and social behaviors, along with dramatic neuroendocrine responses. The vomeronasal transmits olfactory information via a pathway of neuronal projections which bypass higher cognitive centers, resulting in innate stereotyped behavioral and neuroendocrine responses. We have constructed libraries from individual sensory neurons from the VNO which has led to the isolation of a family of perhaps 100 receptor genes that are likely to encode the mammalian pheromone receptors. Interestingly, these genes share homology to the mammalian prostaglandin receptors. The immediate aims of this proposal are to: 1. Identify the chemical nature of mammalian pheromones, specifically testing whether lipid metabolites, such as eicosanoids, serve as pheromones in mammals. 2. Examine the mechanisms by which pheromone binding is transduced to electrical signals within the vomeronasal organ and determine how pheromone stimulation alters synaptic with the accessory olfactory bulb. 3. Associate specific pheromones with specific receptors and with specific behaviors. Ultimately we expect to be able to use this information to deduce a logic by which receptor activation can elicit specific behaviors.